The present invention relates to an automatic radioisotope filling apparatus for minimizing the radiation exposure of the operator of the apparatus. More particularly, the present invention relates to an automatic radioisotope filling apparatus for minimizing the radiation exposure which the operator of the apparatus undergoes, wherein (a) a radioisotope solution is measured for specific radioactivity, (b) if necessary, the radioisotope solution is diluted with a physiological saline solution to adjust the specific radioactivity to a desired level, then (c) a predetermined amount of the radioisotope solution or the diluted radioisotope solution is automatically filled in a label vial containing a drug.
A drug labeled with an radioisotope (hereinafter referred to as a RI and the drug is hereinafter referred to as a labeled drug), when injected into a human body, is selectively collected in a particular tissue or internal organ of the body, depending upon the type of the labeled drug. Examination of the condition by an appropriate detector makes it possible to obtain the physiological or pathophysiological information of the tissue or internal organ in question.
Many nuclides are used as RIs for labeling. Of them, techneticum 99m (Tc-99m) is used in a largest amount. Tc-99m is a daughter nuclide of Mo-99 and has a short half life of 6 hours. Therefore, Tc-99m is obtained, when required, in a form of a RI solution containing Tc-99m, from an apparatus generally called a technegenerator which contains Mo-99 and its daughter nuclide, namely, Tc-99m and from which only Tc-99m can be taken out selectively. As a matter of course, the specific radioactivity of the RI solution taken out from the technegenerator varies by the time period since the production of the technegenerator or by the producer. Accordingly, the specific radioactivity of the RI solution must be measured correctly in order to prepare a labeled drug of a desired amount. Further, it is necessary in some cases to dilute the RI solution with a physiological saline solution to adjust the specific radioactivity of the former to a desired level.
Preparation of a labeled drug has been manually conducted by measuring the radioactivy intensity of a RI solution contained in a RI vial, separately measuring the amount of the RI solution visually in most cases, calculating the specific radioactivity of the solution from its radioactive intensity and amount both obtained above, and filling a required amount of the RI solution into a vial containing a drug by means of a syringe or the like.
Such manual handling of RI has been defective in that the operator undergoes a large radiation exposure as a result of such an operation over a long period of time and may possibly have a serious hazard.
Hence, Japanese Patent Application Laid-Open No. 51400/1984 disclosed an apparatus wherein the manual handling of RI by operator is improved in order to reduce the radiation exposure the operator undergoes.
According to the apparatus, a predetermined amount of a technetium solution or a physiological saline solution is automatically filled into a label vial containing a drug, from a technetium vial containing the technetium solution or from a saline vial containing the physiological saline solution, by the action of a flow controller provided in the middle of a filling path. Therefore, the apparatus has an advantage of being able to substantially reduce the radiation exposure which the operator undergoes.
However, the apparatus disclosed in Japanese Patent Application Laid-Open No. 51400/1984 is defective in the following points. That is, the apparatus has no stirrer for sufficiently reacting the RI solution filled into the label vial with the drug contained in the vial and therefore the label vial must then be transferred to a separate apparatus for stirring. At this time, the operator cannot avoid radiation exposure. Further, the operator of Japanese Patent Application Laid-Open No. 51400/1984 has no means for measuring the specific radioactivity of the technetium solution in the technetium vial and accordingly the specific radioactivity must be measured and calculated using a separate means before the technetium vial is used in the apparatus. Furthermore, the apparatus accomodates only one label vial and, in preparing a plurality of label vials, it is necessary to remove the label vial which has completed filling and to set a new label vial. This exchange operation induces radiation exposure to the operator and moreover makes the whole operation very complicated.
Hence, the object of the present invention is to provide an automatic RI filling apparatus which can minimize the radiation exposure which the operator of RI solution undergoes.
Other object of the present invention is to provide an automatic RI filling apparatus which can prepare a plurality of label vials continuously.
Still other objects and advantages of the present invention will become apparent from the following descriptions.